IIRC, the cutting edge of PWAs when the app store was taking off was Backbone.js, which I don't recall being pleasant enough to work with to want to make anything large in.
I worked on converting an existing knockoutjs SPA into a PWA around that time. I won't claim it was a pleasant experience but it was probably a lot easier and quicker than a small team of webdevs learning mobile dev and cheaper than a new hire. It wasn't a small or basic app, but we did have the advantage of it being a B2B tool that would only be used on android tablets. IIRC it was going to be either extra work or maybe even impossible to get the same functionality on iOS/safari at the time so we just didn't.
React was open sourced in 2013. Service workers, which I consider to be essential to what we understand as PWAs, shipped first in Chrome in 2015, Safari in 2018.
I completely understand the confusion, but "Progressive Web App" or PWA[1], coined by Alex Russell and Frances Berriman[2], has become a specific term for websites that work normally on a pc but can also take advantage of things like push notifications and be installed on the home screen of a phone. You can see a measurable uptick on Google Trends after this blogpost [3].